SERIALIZABLE and INSERTs with multiple VALUES

Hi All,

I notice the following oddity:

=# CREATE TABLE with_pk (i integer PRIMARY KEY);CREATE TABLE

=# BEGIN;BEGIN
=# INSERT INTO with_pk VALUES (1) ON CONFLICT DO NOTHING;INSERT 0 1
=# INSERT INTO with_pk VALUES (1) ON CONFLICT DO NOTHING;INSERT 0 0
=# END;COMMIT

=# BEGIN;BEGIN
=# INSERT INTO with_pk VALUES (2), (2) ON CONFLICT DO NOTHING;
ERROR: could not serialize access due to concurrent update
=# END;ROLLBACK

How are these two transactions different?

Kind Regards,

Jason Dusek
​